The present invention relates to a catheter for use in the practice of medicine.
Catheters have long been utilized in medical practice and are designed for insertion into blood vessels and similar passageways or cavities in the body, to permit infusing or withdrawing fluids or to maintain the openness of an existing passageway into the existing vessel or cavity for subsequent infusion or withdrawal of fluids. The catheter is normally mounted on a cannula for insertion into the body and, when the cannula has pierced the vessel or cavity, the catheter is moved into position so as to maintain the opening when the cannula is withdrawn.
My U.S. Pat. No. 4,917,669 utilizes a novel catheter inserter construction to avoid transmission of infection due to contact by the medical personnel with contaminated blood on a cannula used to insert the catheter. In this patent, a housing completely encloses the cannula after the catheter-carrying cannula, which has been inserted into the patient's vein, is retracted into the housing, leaving the catheter in place. The catheter inserter is then removed from the catheter assembly. However, conventionally, when the cannula is removed, the catheter permits blood from the vein to flow back through the catheter and out onto the patient, bedding, etc., thereby potentially contaminating materials to be handled by others, as well as creating aesthetic problems. This problem may be minimized during the removal of the cannula from the catheter by one of the attendant medical personnel placing a finger on the catheter at the point where the catheter enters the skin, or slightly there beyond, so as to stop the flow of blood manually while the cannula is withdrawn. However, removal of the pressure will permit the subsequent backflow of blood through the catheter.
U.S. Pat. No. 4,894,052 describes a catheter in which this problem exists. In the device shown in U.S. Pat. No. 4,894,052, it is necessary to apply the pressure on the catheter in order to prevent the back flow of blood through the device after a cannula-carrying plug, which has been inserted into the holder for the catheter, is withdrawn from the patient's vein to withdraw the cannula, while an appropriate medical device, such as a fluid transmission line by which the fluid to be infused in the patient's vein, is being connected to the catheter holder at the open end by means of complementary luer-type fittings. See column 7, lines 11-16, 65-66, and column 8, lines 30-41 thereof. However, this procedure is somewhat difficult, since the attendant is required to maintain the pressure on the catheter to prevent back flow with one hand at the same time that the luer fittings are being mated with each other, or, alternatively, two attendants are required, one to mate the luer fittings and the other to apply the pressure on the catheter to stop the blood flow.
An early attempt to solve this problem is illustrated in U.S. Pat. No. 3,915,168, in which a resealable rubber or plastic tube is used for connecting the fluid administration apparatus to the catheter. The tube is bent so as to permit the insertion of the cannula through the side wall of the tube into the catheter to the puncture the vein. The cannula is then withdrawn from the vein through the sidewall of the tube, the tube resealing upon withdrawal. However, this device does not contemplate protection of the contaminated needle after withdrawal, and requires a certain amount of manual dexterity and skill in order to cause the needle, when inserted through the flexible tubing, to pass through the small central bore in the catheter carrying hub to enter the catheter.
U.S. Pat. No. 4,842,591 illustrates a catheter assembly intended to avoid this problem. This device has a catheter housing through which a fluid passage extends. A resilient septum with a preformed slit is mounted in the fluid passage so as to seal the passage. When a syringe is inserted into the catheter housing, a movable annular plug, which is disposed upstream from the septum, is engaged by the syringe so as to be forced downstream against the septum, thereby opening the septum slit to permit the passage therethrough of the liquid expelled from the syringe. Upon withdrawal of the syringe, the septum resiliency returns the annular plug to its original upstream position, so as to permit the septum slit to seal. This device suffers inherently in having a preformed slit, which may be subject to leakage, in addition to presenting difficulties in its economical manufacture by reason of the two-section housing utilized in order to accommodate the disk-shaped septum. Utilizing an annular plug to open the preformed septum slit appears to require the substantial thickness of the septum illustrated in U.S. Pat. No. 4,842,591 to provide the resiliency necessary for the closure of the septum slit upon removal of the syringe. Thus, a septum slit design appears to be inherently susceptible to leakage through the slit, particularly in repetitive use.
In U.S. Pat. No. 4,657,536, there is shown a catheter having a check valve-type termination, intended specifically for use with implanted infusion pumps and the like, where substantially high fluid pressure is generated. In this device, the catheter tip is plugged by a solid plug, and a bore form transversely there across upstream of the plug. An elastic sleeve encloses the catheter tip so as to seal the transverse bore. When inserted in the patient, the elastic sleeve prevents back flow, while permitting forward flow when the fluid is sufficiently pressurized to expand the sleeve. However, this type of device is not suited for use as an intravenous catheter, since the catheter tip is plugged, thereby precluding the insertion of the cannula through the catheter for use in insertion of the catheter into the patient's vein.